HR: 0800h
AN: GP11A-0005    [Abstracts]
TI: No Apparent Polar Wander of Tarim Since the Carboniferous?
AU: * Gilder, S
EM: gilder@ipgp.jussieu.fr
AF: Institut de Physique du Globe de Paris, 4 place Jussieu, Paris cedex 05, IdF 75252 France
AU: Chen, Y
EM: Yan.chen@univ-orleans.fr
AF: Universite d'Orleans, Departement des Sciences de la Terre, Orleans cedex 2, 45067 France
AU: Gomez, J
EM: julia.gomez@ens-lyon.fr
AF: Institut de Physique du Globe de Paris, 4 place Jussieu, Paris cedex 05, IdF 75252 France
AU: Courtillot, V
EM: courtil@ipgp.jussieu.fr
AF: Institut de Physique du Globe de Paris, 4 place Jussieu, Paris cedex 05, IdF 75252 France
AU: Cogne, J
EM: cogne@ipgp.jussieu.fr
AF: Institut de Physique du Globe de Paris, 4 place Jussieu, Paris cedex 05, IdF 75252 France
AB: We report new Permian and Lower to Middle Jurassic paleomagnetic results from the Tarim Block. The Permian red beds pass the fold test, and all samples have reverse polarities, consistent with acquisition of magnetic remanence during the Kiaman Reversed Polarity Superchron. Lower to Middle Jurassic marly limestones also possess a magnetic component characterized by solely reverse polarities and a positive fold test. However, the solely reversed polarities pose a problem because the Lower to Middle Jurassic is thought to have one of the highest reversal frequencies in Earth`s history. Rock magnetic experiments argue for an early-diagenetic age for the magnetization. Together, these new results add to the plethora of paleomagnetic data for Tarim, which is represented by a quasi-continuous time sequence of paleomagnetic poles since the Permo-Carboniferous. After accounting for local vertical axis block rotations and inclination shallowing effects, we find that Tarim has experienced virtually no apparent polar wander since the Carboniferous. Tarim`s apparent polar wander path (APWP) is significantly different than the Eurasian APWP, and a comparison of the two imposes geologically unrealistic tectonic displacements. This leads to the Tarim APWP paradox: are most of the Tarim rocks overprinted, or is the Eurasian APWP not representative of the land east of the Ural Mountains? If the latter is true, then previous tectonic reconstructions must be reconsidered. If the former is true, then when/how can we rely on the paleomagnetic data?
DE: 1519 Magnetic mineralogy and petrology
DE: 1525 Paleomagnetism applied to tectonics: regional, global
DE: 1533 Remagnetization
DE: 8157 Plate motions: past (3040)
SC: Geomagnetism and Paleomagnetism [GP]
MN: Fall Meeting 2005